This invention relates to fuel injection pumps for internal combustion pumps, and more particularly to a fuel injection pump of this kind, which is free from erosion of the pump housing and therefore has a prolonged effective life.
An in-line type fuel injection for use with Diesel engines has a pump housing formed therein with a plurality of pump accommodating spaces arranged in a line, each of which accommodates a pump element comprised of a plunger barrel and a plunger for reciprocating motion in the plunger barrel. The pump element is supported by an element holder in a manner hung therefrom, which also supports a delivery valve holder holding a delivery valve within the element holder. An annular fuel chamber is defined between the pump accommodating space of the pump housing and the plunger barrel, which communicates, on one hand, with a fuel intake hole formed in the pump housing, and on the other hand, with a delivery chamber defined between the plunger and the plunger barrel, through a feed hole formed in the plunger barrel, respectively. With this arrangement, as the plunger makes a reciprocating motion in the plunger barrel, fuel is sucked into the delivery chamber through the fuel intake hole, the fuel chamber and the feed hole, and pressurized therein and delivered through the delivery valve to be injected into an associated engine. Immediately upon completion of each delivery stroke of the plunger, pressurized fuel flows back from the delivery chamber into the fuel chamber through the feed hole, colliding with a portion of the inner peripheral surface of the pump housing facing the feed hole. As a consequence, the same portion of the inner peripheral surface becomes eroded by the pressurized fuel. The degree of erosion is high particulary in a pump housing made of a material having low hardness such as aluminum.
In order to avoid such erosion, in a conventional in-line type fuel injection pump, an annular deflector is fitted around the plunger barrel and disposed within the fuel chamber at a location opposite the feed hole. Such deflector is formed with a suitable number of through holes for passing fuel therethrough, and fitted with low rigidity around the plunger barrel for facilitation of the mounting of same. Therefore, after the lapse of some time of use, the deflector becomes dislocated in circumferential position so that one of the above through holes formed therein and the feed hole become circumferentially and axially aligned with each other. Consequently, upon completion of each delivery stroke of the plunger, fuel ejected through the feed hole strikes directly against the inner peripheral surface of the pump housing, causing erosion of same. Thus, erosion of the pump housing cannot be positively prevented even with such deflector.
Further, the pump housing of the conventional fuel injection pump is also formed therein with a space for receiving a fuel control rod for adjusting the effective delivery stroke of the plunger, as well as with a fuel chamber. Therefore, the pump housing has rather a complicate configuration, resulting in a high manufacturing cost of the pump.